This invention relates to a process for preparing alkyl diaminopropanes. More particularly, this invention relates to a process for the production of C.sub.10 and higher alkyl-1,3-diaminopropanes from C.sub.10 and higher alkyl aminopropionitriles.
In general, alkyl nitriles can be catalytically reduced to primary alkyl amines over a wide range of operating conditions. The process, however, produces as by-products significant amounts of secondary and tertiary amines. In an effort to improve the selectivity to primary amine products while reducing secondary and tertiary amine by-products, U.S. Pat. Nos. 2,160,578 and 2,165,515 describe procedures conducted under essentially isothermal conditions and in the presence of ammonia or low molecular weight amines. British Pat. No. 855,027 proposes that the formation of secondary and tertiary amines can be suppressed by carrying out the hydrogenation in the vapor phase using a hydrogenation catalyst in fluidized form. More recently, U.S. Pat. No. 3,163,676 discloses that improved results can be obtained by recycling the finished primary amine product to the hydrogenation zone thereby reducing the amount of secondary and tertiary amines formed.
With regard to the catalytic reduction of C.sub.10 and higher alkyl aminopropionitriles to the corresponding alkyl diaminopropanes the reaction is exothermic in nature. Upon conducting the process in small or laboratory size reactors, the heat of reaction is easily dissipated through the reactor walls. Under such essentially isothermal conditions, the heat of reaction does not significantly affect the selectivity of the process. However, the heat of reaction is substantially retained in the liquid phase when larger or commercial size reactors are employed which in turn adversely affects the process selectivity. More particularly, we have found that the reaction is influenced by various equilibrium relationships wherein at lower temperatures partially reduced nitrile intermediate products react with formed primary amine product to produce undesirable secondary and tertiary amine by-products. At higher reaction temperatures, cracking of the molecule occurs wherein the alkyl aminopropionitriles are converted to lower molecular weight primary amines and propionitriles. While the reaction conditions, particularly the reaction temperature, can be controlled by external cooling means or through the use of various devices in the reaction zone, as by cooling coils, such means or devices can often times cause processing interruptions due to mechanical failures. A highly desirable process would be one capable of providing selective conversion of the nitrile to the alkyl diaminopropane, of being employed in a simple reactor design and with the ability of the process to self regulate the reaction temperature by the removal of heat from the liquid reactants in the reaction zone.
It is therefore an object of this invention to provide a process for the catalytic reduction of C.sub.10 and higher alkyl aminopropionitriles to C.sub.10 and higher alkyl-1,3-diaminopropanes.
Another object of this invention is to provide a process for selectively converting C.sub.10 and higher alkyl aminopropionitriles to C.sub.10 and higher alkyl-1,3-diaminopropanes.
Yet another object of this invention is to provide a process for the catalytic hydrogenation of C.sub.10 and higher alkyl aminopropionitriles to C.sub.10 and higher alkyl-1,3-diaminopropanes in high yields.
Yet another object of this invention is to provide a continuous catalytic hydrogenation process wherein C.sub.10 and higher alkyl aminopropionitriles are reduced to C.sub.10 and higher alkyl-1,3-diaminipropanes while simultaneously deterring the cracking to lower molecular weight primary amines and the formation of secondary and tertiary amines.
Other objects and advantages will become apparent from a reading of the following detailed description of the invention.